Watch makers rarely use the term "waterproof": https://www.hodinkee.com/articles/why-no-watch-is-waterproof. For a time, the FTC banned this.
The Fenix 6 is also 10ATM water resistant. ISO says a dive watch must be rated to at least 10ATM, but honestly: if you're going diving, you can just take off your smartwatch, since you'll want a dive computer anyway.
1. It has all the health monitoring things (heart rate, ECG, oximeter, sleep).
2. It has 30 day battery life.
3. It has a sapphire glass (scratch resistant).
4. It has 10 ATM water resistance (100 meters/330 feet).
On the other hand, the screen part of this watch seems very small, it doesn't run a standard smartwatch OS, and the water resistance isn't an outright claim of being waterproof (so likely OK for swimming but not scuba diving). An alternative like the Garmin Fenix (https://www.garmin.com/en-US/p/641479/pn/010-02158-13) seems more practical in terms of screen size, although it is pricier and doesn't have the oximeter.